The use of p-toluene sulfonate to dissolve synaptosomal membrane proteins into organic solvents

A method is described by which a large proportion of membrane proteins may be dissolved in organic solvents by the use of p-toluene sulfonate. Synaptosomal membrane fractions from rat cerebral cortex were used as test material. Chloroform-methanol extraction dissolved 7% of proteins, 89% of lipid phosphorus, and 35% of reducing sugars. Further extraction of the residue with 2.5 mm p-toluene sulfonate in chloroform-methanol allowed the dissolution of 45% of the proteins. The final residue contained the rest of the protein and 60% of reducing sugars. The polypeptides in the three fractions showed marked differences in molecular weight and several glycoprotein bands were found in the final residue. The amino acid content of these three protein fractions was also different. It is concluded that p-toluene sulfonate, by lowering the pH and binding to the positive charges in the protein, is able to transfer about half of the synaptosomal membrane proteins into a hydrophobic medium.     

Hybrids of Xenopus laevis and Xenopus borealis express proteins from both parents.

Xenopus laevis and X. borealis oocytes were compared by two-dimensional electrophoresis of radioactive proteins. At least one-third of the major newly synthesized proteins differ in their electrophoretic mobility. Protein-coding genes from both parents are expressed in interspecific hybrids, thereby providing useful genetic markers for a variety of embryological studies.     

Nucleocytoplasmic distribution of snRNPs and stockpiled snRNA-binding proteins during oogenesis and early development in Xenopus laevis

The distribution of small nuclear ribonucleoprotein particles containing U snRNAs (U snRNPs) during oogenesis and early development in Xenopus was analyzed with a lupus antibody (anti-Sm) that reacts with snRNA-binding proteins. Fully grown oocytes and embryos prior to gastrulation were found to be relatively depleted of U snRNPs in their nuclei and to contain an excess of snRNA-binding proteins stored in the cytoplasm. During late blastula-early gastrula, or after microinjection of U snRNAs into the cytoplasm of a mature oocyte, the proteins migrate into the nucleus. Dot hybridization analysis showed that small previtellogenic oocytes already contain a maximal amount of U1 (and U2) snRNAs, which then decreases to about 20% of that value in fully mature oocytes, even though the cell's volume has increased enormously. Thus fully grown oocytes and eggs accumulate snRNA-binding proteins for use during early development, but this is not coupled with the accumulation of U snRNA.     

Gradients of homeoproteins in developing feather buds

Homeoproteins are functionally involved in pattern formation. Recently, homeoproteins have been shown to be distributed in a graded fashion in developing limb buds. Here we examine the expression of homeoproteins in chicken feather development by immunocytochemical localization. We find that XlHbox 1 antigen is present in cell nuclei and is distributed in a gradient in the mesoderm of developing feather buds, with strongest expression in the anterior-proximal region. The gradient is most obvious in feather buds from the mid-trunk level. Feather buds from the scapular level express very high levels of XlHbox 1 and feather buds from the caudal region express no XlHbox 1, suggesting that a broad gradient along the body axis is superimposed on a smaller gradient within each individual feather bud. Feather ectoderm also expresses XlHbox 1 antigen but without an obvious graded pattern. Another homeoprotein, Hox 5.2, is also expressed in developing feather buds in a graded way, and its distribution pattern is partially complementary to that of XlHbox 1. These observations suggest that homeoproteins may be involved in setting up the anteroposterior polarity of cell fields at different levels, first for the body axis, then for the limb axis and finally for the feather axis.